The present invention relates to a method for recovering carbon dioxide, in which in a thermal electric power plant, carbon dioxide contained in combustion exhaust gas of boiler is removed and recovered, and a system therefor.
In power generating equipment in a thermal electric power plant using large quantities of fossil fuel, as a method for removing and recovering carbon dioxide (CO2), which is one cause for global warming, an amine absorption process has been used (for example, see Japanese Patent Provisional Publication No. 8-257355). However, the amine absorption process has a problem of requiring thermal energy from a large amount of low-pressure steam (for example, about 0.3 MPa) to regenerate an absorbing solution having absorbed CO2. On the other hand, there have been developed a technique for fixing recovered CO2 under pressure in an underground aquifer, a technique for injecting CO2 under pressure into an oil field, a technique for injecting CO2 under pressure into a deep coal seam to recover methane in the coal seam, and other techniques. However, in order to inject CO2 under pressure, it is necessary to compress CO2 to a high pressure (for example, about 140 kg/cm2G), and when a power source for such compression is secured, the output of power plant inevitably decreases significantly.